--- /dev/null
+From: Gregory CLEMENT <gregory.clement@free-electrons.com>
+Date: Thu, 4 Feb 2016 22:09:29 +0100
+Subject: [PATCH] net: mvneta: Fix race condition during stopping
+
+When stopping the port, the CPU notifier are still there whereas the
+mvneta_stop_dev function calls mvneta_percpu_disable() on each CPUs.
+It was possible to have a new CPU coming at this point which could be
+racy.
+
+This patch adds a flag preventing executing the code notifier for a new
+CPU when the port is stopping. It also uses the spinlock introduces
+previously. To avoid the deadlock, the lock has been moved outside the
+mvneta_percpu_elect function.
+
+Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+
+--- a/drivers/net/ethernet/marvell/mvneta.c
++++ b/drivers/net/ethernet/marvell/mvneta.c
+@@ -374,6 +374,7 @@ struct mvneta_port {
+ * ensuring that the configuration remains coherent.
+ */
+ spinlock_t lock;
++ bool is_stopped;
+
+ /* Core clock */
+ struct clk *clk;
+@@ -2853,16 +2854,14 @@ static void mvneta_percpu_disable(void *
+ disable_percpu_irq(pp->dev->irq);
+ }
+
++/* Electing a CPU must be done in an atomic way: it should be done
++ * after or before the removal/insertion of a CPU and this function is
++ * not reentrant.
++ */
+ static void mvneta_percpu_elect(struct mvneta_port *pp)
+ {
+ int elected_cpu = 0, max_cpu, cpu, i = 0;
+
+- /* Electing a CPU must be done in an atomic way: it should be
+- * done after or before the removal/insertion of a CPU and
+- * this function is not reentrant.
+- */
+- spin_lock(&pp->lock);
+-
+ /* Use the cpu associated to the rxq when it is online, in all
+ * the other cases, use the cpu 0 which can't be offline.
+ */
+@@ -2906,7 +2905,6 @@ static void mvneta_percpu_elect(struct m
+ i++;
+
+ }
+- spin_unlock(&pp->lock);
+ };
+
+ static int mvneta_percpu_notifier(struct notifier_block *nfb,
+@@ -2920,6 +2918,14 @@ static int mvneta_percpu_notifier(struct
+ switch (action) {
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
++ spin_lock(&pp->lock);
++ /* Configuring the driver for a new CPU while the
++ * driver is stopping is racy, so just avoid it.
++ */
++ if (pp->is_stopped) {
++ spin_unlock(&pp->lock);
++ break;
++ }
+ netif_tx_stop_all_queues(pp->dev);
+
+ /* We have to synchronise on tha napi of each CPU
+@@ -2957,6 +2963,7 @@ static int mvneta_percpu_notifier(struct
+ MVNETA_CAUSE_LINK_CHANGE |
+ MVNETA_CAUSE_PSC_SYNC_CHANGE);
+ netif_tx_start_all_queues(pp->dev);
++ spin_unlock(&pp->lock);
+ break;
+ case CPU_DOWN_PREPARE:
+ case CPU_DOWN_PREPARE_FROZEN:
+@@ -2981,7 +2988,9 @@ static int mvneta_percpu_notifier(struct
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ /* Check if a new CPU must be elected now this on is down */
++ spin_lock(&pp->lock);
+ mvneta_percpu_elect(pp);
++ spin_unlock(&pp->lock);
+ /* Unmask all ethernet port interrupts */
+ on_each_cpu(mvneta_percpu_unmask_interrupt, pp, true);
+ mvreg_write(pp, MVNETA_INTR_MISC_MASK,
+@@ -3033,7 +3042,7 @@ static int mvneta_open(struct net_device
+ */
+ on_each_cpu(mvneta_percpu_enable, pp, true);
+
+-
++ pp->is_stopped = false;
+ /* Register a CPU notifier to handle the case where our CPU
+ * might be taken offline.
+ */
+@@ -3066,9 +3075,18 @@ static int mvneta_stop(struct net_device
+ {
+ struct mvneta_port *pp = netdev_priv(dev);
+
++ /* Inform that we are stopping so we don't want to setup the
++ * driver for new CPUs in the notifiers
++ */
++ spin_lock(&pp->lock);
++ pp->is_stopped = true;
+ mvneta_stop_dev(pp);
+ mvneta_mdio_remove(pp);
+ unregister_cpu_notifier(&pp->cpu_notifier);
++ /* Now that the notifier are unregistered, we can release le
++ * lock
++ */
++ spin_unlock(&pp->lock);
+ on_each_cpu(mvneta_percpu_disable, pp, true);
+ free_percpu_irq(dev->irq, pp->ports);
+ mvneta_cleanup_rxqs(pp);
+@@ -3339,7 +3357,9 @@ static int mvneta_config_rss(struct mvn
+ mvreg_write(pp, MVNETA_PORT_CONFIG, val);
+
+ /* Update the elected CPU matching the new rxq_def */
++ spin_lock(&pp->lock);
+ mvneta_percpu_elect(pp);
++ spin_unlock(&pp->lock);
+
+ /* We have to synchronise on the napi of each CPU */
+ for_each_online_cpu(cpu) {
projects / openwrt / openwrt.git / blobdiff